From documentation for setKeepAliveTimeout:handler: method of UIApplication:
In iOS 8 and later, voice-over-IP (VoIP) apps register for UIRemoteNotificationTypeVoIP push notifications instead of using this method. Using push notifications eliminates the need for a timeout handler to check in with the VoIP service. Instead, when a calls arrives for the user, the VoIP service sends a VoIP push notification to the user’s device. Upon receiving this notification, the device launches or wakes the app as needed so that it can handle the incoming call.
But I can't find anything about it. Is this a thing?
If someone is also confused by this documentation, they probably mean PushKit Framework and PKPushTypeVoIP presented in WWDC 2014, Writing Energy Efficient Code, Part 2